Honey bee pollination is crucial to a variety of crops, but honey bees are afflicted by a variety of pests and diseases. American foulbrood (AFB), a disease caused by Paenibacillus larvae, is arguably the most devastating of these diseases. AFB results in multi-million losses to the beekeeping industry, and is a likely contributing factor to Colony Collapse Disorder.
AFB kills developing honey bee larvae (White, “The bacteria of the apiary, with special reference to bee diseases,” GPO, Washington, 1906; and Broodsgaard et al., Apidologie 29:569-578, 1998). P. larvae spores are the infectious agent for AFB, but it is the vegetative cells that cause disease (Genersch, J. Invertebr. Pathol., 103:S10-S19, 2010; and Tarr, Ann. Appl. Biol., 25:807-814, 1938).
In 2005, a survey of almond pollinating bee colonies indicated 4% of colonies had significant AFB load (Eischen and Graham, Am. Bee. J., 145:390-391, 2005). Once a beekeeping operation is contaminated, the bacterial spores are not easily removed (Shimanuki, “Identification and control of honey bee diseases,” U.S. Dept. of Agriculture, Washington D.C., 1983). Although autoclaving and high concentrations of chemical disinfectants effectively kill spores, these treatments are not viable for the bee keeping industry (Dobbelaere et al., J. Appl. Microbiol., 91:212-216, 2001). In the United States, AFB typically is treated with prophylactic use of antibiotics (e.g., terramycin). However, the spore stage of P. larvae is not affected by antibiotic treatment, and the use of antibiotics can lead to resistant strains (Alippi, Vet. Microbiol., 125:290-303, 2007; and Lodesani and Costa, Bee World, 86:102-109, 2005). Further, antibiotic treatment can leave residue in wax and honey, and many countries ban the use of antibiotics. Thus, burning of infected colonies and beekeeping equipment has been the only accepted practice for controlling the spread of AFB (Genersch, supra; and Shimanuki, supra).